Oil Sands Tailings Ponds
Water and solvents are required to extract bitumen from mined oil sands. This water, prostate along with sand and clay from the ores plus unrecovered bitumen and solvent, online is stored in large ponds (tailings ponds) that allow the clay particles to settle so the water can be reused. Due to the large volume of oil sands processed and a policy of ‘zero discharge’, viagra the tailings ponds currently cover around 176 square kilometers and contain approximately 840 million cubic meters of tailings, a volume that increases each year. It is the goal of operators to close these ponds and return the land to its natural state as soon as possible. In addition to using up space and water, substantial volumes of methane and carbon dioxide are produced by natural communities of microbes that live in the ponds; these greenhouse gases (GHG) escape into the atmosphere at the surface of the ponds.
· Safe Tailings Pond Closure
It is the goal of tailings pond operators to close active tailings ponds so the land can be remediated. To do this, operators must remove the bulk of the water and cover the tailings with soil. However, tailings ponds contain a wide range of microorganisms that can produce toxic compounds such as hydrogen sulfide and gases like methane and carbon dioxide that can compromise the safety and stability of the covered tailings. By documenting and understanding how the activities of the microbial communities present in oil sand tailings ponds change when tailings ponds are closed, project investigators have assisted tailings pond operators in determining that their tailings ponds can be safely closed and remediated.
· Greenhouse Gas (GHG) Emissions
Project researchers have determined that communities of bacteria called ‘methanotrophs’ are active on the surface of some oil sands tailings ponds. These methanotrophs eliminate methane (a potent GHG) by oxidizing it to water and carbon dioxide (a less-potent GHG). The project has estimated that, when present, methanotrophs can remove up to 50% of the methane emissions produced by the tailing ponds microbes. Ensuring that methanotrophs are active in all tailings ponds where methane gas is emitted can help reduce the negative impact tailings ponds have on GHG emissions.
The project has isolated several very potent biosurfactants (natural ‘detergents’) produced by tailings pond bacteria, which can be now be produced in E. coli. Surfactants have a wide range of uses and biosurfactants have the added advantage of being inexpensive to produce, non-toxic and biodegradable. It is envisioned that these biosurfactants could be used to accelerate water recovery from oil sands tailings and extraction of residual bitumen from tailings ponds.
Monitoring and repairing corrosion damage in iron pipelines and storage facilities costs the oil and gas industry billions each year and corrosion damage can lead to dangerous and toxic pipeline failures.
· Understanding Corrosion
Although it has been known for some time that sulfate-reducing organisms can accelerate pipeline corrosion, the project’s metagenomic studies are identifying novel organisms, such as methanogenic Archaea that can also contribute to corrosion. By analyzing the microbial communities that accelerate pipeline corrosion, the project is identifying a catalogue of microorganisms that operators can use to help predict corrosion risk.
· Controlling Corrosion
Metagenomic studies discovered that the addition of bisulphite to pipelines was fueling metal corrosion mediated by sulfate-reducing bacteria. By phasing out the excessive use of bisulphite in a critical water system feeding a steam-assisted gravity drainage (SAGD) oil sands operation, the operator was able to significantly reduce the impact of microbially-influenced corrosion on their infrastructure.
Tailings ponds contain many toxic compounds, such as naphthenic acids and residual bitumen that must be remediated before ponds can be reclaimed.
· Toxicity Reduction
The project has identified members of the indigenous microbial communities capable of degrading many of the toxic compounds in tailings ponds. These microorganisms are now being isolated for use in the development of sensors and for remediation applications.
Souring is the process where the microbial community in an oil reservoir converts sulfate to hydrogen sulfide (H2S), which is a highly toxic, smelly and corrosive chemical. Dealing with elevated levels of H2S is not only expensive and hazardous, it can jeopardize the operator’s license to operate.
· Souring Control
By sequencing the DNA of microbial communities in produced water samples collected from Alberta oil fields, the project has monitored how the microorganisms responsible for souring respond when the field is treated with biocides and other compounds designed to inhibit souring. This has helped the operators determine the best dosage size and interval for optimal souring control, by targeting the microbes responsible for this undesirable activity.